Association between fetal sex, birthweight percentile and adverse pregnancy outcome.

INTRODUCTION: The objective was to evaluate the association between fetal sex and adverse pregnancy outcome, while correcting for fetal growth and gestational age at delivery. MATERIAL AND METHODS: Data from the Netherlands Perinatal Registry (1999-2010) were used. The study population comprised all white European women with a singleton delivery between 25+0 and 42+6  weeks of gestation. Fetuses with structural or chromosomal abnormalities were excluded. Outcomes were antepartum death, intrapartum/neonatal death (from onset of labor until 28 days after birth), perinatal death (antepartum death or intrapartum/neonatal death), a composite of neonatal morbidity (including infant respiratory distress syndrome, sepsis, necrotizing enterocolitis, meconium aspiration, persistent pulmonary hypertension of the newborn, periventricular leukomalacia, Apgar score <7 at 5 minutes, and intracranial hemorrhage) and a composite adverse neonatal outcome (perinatal death or neonatal morbidity). Outcomes were expressed stratified by birthweight percentile (p90 [large for gestation]) and gestational age at delivery (25+0 -27+6 , 28+0 -31+6 , 32+0 -36+6 , 37+0 -42+6  weeks). The association between fetal sex and outcome was assessed using the fetus at risk approach. RESULTS: We studied 1 742 831 pregnant women. We found no increased risk of antepartum, intrapartum/neonatal and perinatal death in normal weight and large-for-gestation males born after 28+0  weeks compared with females. We found an increased risk of antepartum death among small-for-gestation males born after 28+0  weeks (relative risk [RR] 1.16-1.40). All males born after 32+0  weeks of gestation suffered more neonatal morbidity than females regardless of birthweight percentile (RR 1.07-1.34). Infant respiratory distress syndrome, sepsis, persistent pulmonary hypertension of the newborn, Apgar score <7 at 5 minutes, and intracranial hemorrhage all occurred more often in males than in females. CONCLUSIONS: Small-for-gestation males have an increased risk of antepartum death and all males born after 32+0  weeks of gestation have an increased risk of neonatal morbidity compared with females. In contrast to findings in previous studies we found no increased risk of antepartum, intrapartum/neonatal or perinatal death in normal weight and large-for-gestation males born after 28+0  weeks.

Birth weight ratio as an alternative to birth weight percentile to express infant weight in research and clinical practice: a nationwide cohort study.

Objective. To compare birth weight ratio and birth weight percentile to express infant weight when assessing pregnancy outcome. Study Design. We performed a national cohort study. Birth weight ratio was calculated as the observed birth weight divided by the median birth weight for gestational age. The discriminative ability of birth weight ratio and birth weight percentile to identify infants at risk of perinatal death (fetal death and neonatal death) or adverse pregnancy outcome (perinatal death + severe neonatal morbidity) was compared using the area under the curve. Outcomes were expressed stratified by gestational age at delivery separate for birth weight ratio and birth weight percentile. Results. We studied 1,299,244 pregnant women, with an overall perinatal death rate of 0.62%. Birth weight ratio and birth weight percentile have equivalent overall discriminative performance for perinatal death and adverse perinatal outcome. In late preterm infants (33(+0)-36(+6) weeks), birth weight ratio has better discriminative ability than birth weight percentile for perinatal death (0.68 versus 0.63, P 0.01) or adverse pregnancy outcome (0.67 versus 0.60, P < 0.001). Conclusion. Birth weight ratio is a potentially valuable instrument to identify infants at risk of perinatal death and adverse pregnancy outcome and provides several advantages for use in research and clinical practice. Moreover, it allows comparison of groups with different average birth weights.

Potential improvement of pregnancy outcome through prenatal small for gestational age detection. [correction].

OBJECTIVE: To assess differences in mode of delivery and pregnancy outcome between prenatally detected and nonprenatally detected small for gestational age (SGA) neonates born at term. STUDY DESIGN: We performed a retrospective multicenter cohort study. All singleton infants, born SGA in cephalic position between 36(0/7) and 41(0/7) weeks gestation, were classified as either prenatally detected SGA or nonprenatally detected SGA. With propensity score matching we created groups with comparable baseline characteristics. We compared these groups for composite adverse perinatal outcome, labor induction, and cesarean section rates. RESULTS: We included 718 SGA infants, of whom 555 (77%) were not prenatally detected. Composite adverse neonatal outcome did not differ statistically significant between the matched prenatally detected and the nonprenatally detected group (5.5 vs. 7.4%, odds ratio [OR] 0.74, 95% confidence interval [CI]: 0.30-1.8). However, perinatal mortality only occurred in the nonprenatally detected group (1.8% [3/163] in the matched cohort, 1.3% [7/555] in the complete cohort). In the propensity matched prenatally detected SGA group both induction of labor (57 vs. 9%, OR 14.0, 95% CI: 7.4-26.2) and cesarean sections (20 vs. 8%, OR 2.9, 95% CI: 1.5-5.8) were more often performed compared with the nonprenatally detected SGA group. CONCLUSION: Prenatal SGA detection at term allows timely induction of labor and cesarean sections thus potentially preventing stillbirth.

Recurrence of small-for-gestational-age pregnancy: analysis of first and subsequent singleton pregnancies in The Netherlands.

OBJECTIVE: Small-for-gestational-age (SGA) neonates are at increased risk of adverse pregnancy outcome. Our objective was to study the recurrence rate of SGA in subsequent pregnancies. STUDY DESIGN: A prospective national cohort study of all women with a structurally normal first and subsequent singleton pregnancy from 1999-2007. SGA was defined as birthweight <5th percentile for gestation. We compared the incidence and recurrence rate of SGA for women in total and with and without a hypertensive disorder (HTD) in their first pregnancy. Moreover, we assessed the association between gestational age at first delivery and SGA recurrence. RESULTS: We studied 259,481 pregnant women, of whom 12,943 women (5.0%) had an SGA neonate in their first pregnancy. The risk of SGA in the second pregnancy was higher in women with a previous SGA neonate than for women without a previous SGA neonate (23% vs 3.4%; adjusted odds ratio, 8.1; 95% confidence interval, 7.8-8.5) and present in both women with and without an HTD in pregnancy. In women without an HTD, the increased recurrence risk was independent of the gestational age at delivery in the index pregnancy; whereas in women with an HTD, this recurrence risk was increased only when the woman with the index delivery delivered at >32 weeks' gestation. CONCLUSION: Women with SGA in their first pregnancy have a strongly increased risk of SGA in the subsequent pregnancy and first pregnancy SGA delivers a significant contribution to the total number of second pregnancy SGA cases.